I did this build a number of years ago, it was a fun one to do as it had a few little niggly challenges that i had to get around.
Firstly i couldnt un-convince the owner to steer cleear of a capacitor and run more batteries or optimaly upgrade the alternator, all options i gave and got turned down on!
He was sold on the idea from a car audio shop and i couldnt sway him, the sales pitch must of been BOMB!
A Lanzar Audio Opti- driven audio installation
The subwoofer of his choice was a Lanzar Opti 12″ a Dual voicecoil, 900wrms driver, with an FS of 29hz and an xmax of 14mm it seemed fitting for the application of playing his favourite genre of RnB and the odd modern mastered commercial record, these days with heavily compressed music program material its very important to have a driver capable of operating within its thermal and mechanical limits. Yesteryears highly dynamic material needed highly sensitive drivers capable of reproducing accurate transients and be tonaly accurate at very dynamic input voltages, today we need sturdy drivers with high mechanical and thermal properties to deal with the lack of dynamics.
The enclosure was built to use the maximum available space it couldnt sit up against the seats as normaly built, he wanted a cubby space on each side for “things” i had to deal with pressure able to escape down the front baffle face and down the sides so some wings were made to compartamentalise the area behind the seat, it was measured and calculated as the skihatch becomes another port making the space behind it another chamber effectively making this a quasi-sixth ordered bandpass enclosure of sorts.
Looking at the diagram below you can see how the box in red is a 4th order the green section becomes another enclosure and the small section of the ski hatch effectively turns into a port here exagerated in blue
The owner provided an array of equipment to get the whole system together without having to make any permanent alterations to the car, He provided Stinger fusing and a split charge relay.
Choosing the JL Audio Cleansweap which is a aftermatket DSP it takes already processed audio signals from standard car radios and converts them into “as best as possible” to a 20-20khz flat EQ response. With line level outputs of 8v and an SNR of 102db it really does a great job of feeding clean audio to your amplifiers, more than twice the ouput voltage you generally get from the Pre outs on a car audio headunit!
It performed well in balancing out the eq, i found it to be a little heavy around 50-60 hertz and figured it to be the natural bump in the mercedez EQ that couldnt be quite flattened perfectly, i took this into acount once i realised the problem whilst desinging the enclosure.
The volume pot for the JL CL441DSP was installed in the glove compartment in a custom made panel.
From memory i belive the component set was from JL Audio, rear tweeters where mounted in a rather convenient location in the parcel shelf and imaged well reflecting off the glass, the fronts where located in the oem location with no modification needed appart from some adjustment to the angle.
The Lanzar amps used where a 2000D monoblock providing more than adequate power, the subwoofer being 900wrms wired in parallel to 1ohm will have a working resistence which will allow the amplifier to function well within not only its power limits but have enough dynamic power to effectively deal with high attack transients or long tailed basslines like 808’s.
Heres the power specs on the 2000D
700 Watts RMS Power @ 4 Ohms
1100 Watts RMS Power @ 2 Ohms
1600 Watts RMS Power @ 1.3 Ohms
As you can see with over 1000wrms at 2ohm we can deliver more than the the recomended power handling of 900wrms when we drop into the lower impedances. The amplifier should not sag or have a transient delay due to a spike in amplitude.
Many manufacturers or installers will aproach a system design with matching sub and amp power ratings, this does nothing but leave the subwoofer with no headroom for transients. This power sag comes from the lack of capacitance inside the amplifiers electronics to deal with a higher current demand than what its capable of. This of course is all depedant on a supporting power supply meeting the current demands.
For the components which i believe were a 60 or 75wrms set the Lanzar 100×4 stereo amplifier was used, with 100watts at 4ohm it was more than capable of driving the mids and tweeters.
The monoblock and four channel are wired with oversized 4awg JL Audio wiring to make sure current delivery was not an issue. Fused using a Stinger SPD5203 ANL and Stinger SGP38 Split Charge kit, Power was evenly distributed to both the OEM and Stinger Power Series Batteries using 0awg from there on to the capacitor housed in the left compartment.
It was something that was added towards the end of the project as an afterthought and against my recomendations. I tested voltage drop across the board in the system before the capacitor was even in my posession to install.
I gain matched the system set the volume at about 80% and the Cleansweeps input and output gains so that SPL levels were high as possible in the cabin across the bandwidth of the system without the voltage dipping too much .
Setting the main Cleansweep external volume pot at roughly an eyeballed 80% ensures that theres always a little headroom to compensate for as we all know those low volume rips off the internet!
Keeping the amps full of current during exclusively sinewave testing ensures that when music program material is used the power demands are much less, this ensures you never exceed the current capicty of the system, again another safe measure used was doing all this at engine idle, this means that the lowest amount of current is delivered by the alternator.
This is a great reference point to start tuning a systems potential, at this stage you can be fairly certain that you will never dip your amps voltage excessively, the amps will always have more than enough current to operate effectively, your sub and speakers will allways recieve a clean undistorted signal as opposed to a saturated amp throwing out all sorts of dirty harmonics.
From this position you can start increasing things finding the limits of each component and adjusting as needed. after about 3 days of testing at these power settings the owner took the car for about a month before returning for a full system tune up. Read on to find out how i learnt about naughty old school tricks of the trade!
I spent another whole day listening and testing the newly broken in system and effectively tried to work through the owners feedback, there was a rattle around 70hz from the parcel shelf that needed dampening, one tweeter needed a slight angle adjustment after increasing the output as reflections off the drivers window where an issue.
Appart from that the EQ was reset, recalibrated and small adjustments to the amplifers filters where applied, the most critical was lowering the subsonic filter to 18hz where now the subwoofer had time to bed in, the mechanical suspension isnt as stiff and power can now be delivered safely.
Setup this way effectively gives you a cheater system, its never working flat out, so essentialy it can always be turned up a little for fun with just a little twist of the cleansweaps volume knob remember that 20% headroom?.
As the ownwer was always going to use the OEM radio volume and steering controls to adjust output he always had the option to push that little bit futher at just the reach of the glovebox, another little push could come from the output gain of the cleansweep as aldready the system is setup to be efficient at idle. When the engine RPM raises the output of the alternator will raise again effictively allowing more current to be drawn from the system.
I do this for one reason only and thats our ears, The ear is incredible at compression, you get used to volume levels over time quite quickly, by giving yourself this headroom you can extend the life cycle of your soundsystem by increasing its output over time, a little trick i learnt way back when!
This may seem counter intuative to alot of people, why would you install a system only to use a small percentage, well theres many reasons, first you get to learn your system over time, it allows you to make small incremental adjustments and lets face it there always going to be adjustments in the postive direction, all the extra amperage an alternator will give at 3000rpm over idle can make a huge difference. if you start off with everything wide open you never really get a feel for how much you can tax your system long term.
Theres an old school car audio shop technique nobody will tell you about!
How do they make things sound so much better sometimes with the simplest of upgrades?… a little fettle with the gains a little adjustment of the filters… boom! pshycoacoustics! the whole system sounds brand new… why? becuase you got used to what it USED to sound like
Check out my Music theory and tutorials to learn more about how this works exactly!